Bug extermination questions

I received this note from a local company here in Ptld. Oregon that we provide milled lumber to. It's one of our largest clients. I thought I'd get some feedback from the experienced experts on how you would answer the questions asked. My thoughts are that a 4-6 hour spike heating of >140 degrees should get the core temp of the wood over 130 degrees and kill any and all bugs?

In an effort to continue providing quality furniture that is as problem free as possible, we would like to establish some standards for buying lumber that best assures us of lumber being free of bugs. One incident of bugs can be a costly endeavor in terms of time, material cost, labor cost and a hit to one’s reputation. With that in mind here are some thoughts we have had regarding the drying process:

• The lumber core must be heated to 130 degrees for at least 2 hrs.
• If the kiln just gets up to 130 degrees it does not mean that the interior reached that temperature to kill off any bugs and eggs.
• To get interior to that temperature usually means that kiln must reach temperatures of something above 130 degrees.
• All vendors must provide return policies for material that has bugs and a time frame for the return of material.

What we are asking of you is

• Are you able to get a core temperature reading?
• Is the 2 hour time at 130 degrees a reasonable time?
• What temperature do you normally try to achieve to eliminate any bug issues?
• What is your policy about returning material if bugs do make an appearance, understanding that bugs may not appear until after a piece of furniture is made and in someone’s home for six months.

(We did some research to come up with the 130 degree temperature. The two hour treat time was a high end preference to make totally sure any bugs were dealt with.)

We would love to have any and all feedback that you are will to provide. I thank you in advance for helping us to continue to provide the best quality furniture and service available.

If you want numbers you could test by drilling a hole into the center of a typical board or two and embedding a probe or thermocouple then seal the hole.

Have you looked on the Wood Web? You can search the knowledge base there. Expert Gene Wengert has written a lot about this, the temperatures, times, etc.

In the knowledge base under "How Much Heat is Enough to Kill Insects?" one person there wrote "According to the DKOM, powder post beetles are killed at temperatures as low as 125F. They show T ranges of 125-130-140. For the lowest temperature, it takes longer, of course, 46-50 hours. " Wengert said 6 hours at 130 would be enough but I think he was verifying the plan the original poster mentioned, but he didn't give a minimum time at the kiln temperature of 130-deg. The table in the DKOM says the kiln temperature needs to be held at 130 for 10-14 hours depending on the wood thickness.

BTW, DKOM is the Dept of Agriculture Forestry Service Dry Kiln Operator's Manual The schedule mentioned is in table 7-31 on page 176 https://www.esf.edu/wus/documents/Dr...torsManual.pdf

Elsewhere I've seen recommended temperatures up to 160 degrees - this was the temperature needed in the kiln to assure the core temperatures reached 130 degrees. Somewhere I read that if the interior of every board reached 130 deg for any length of time all insects would be killed so if that is true 2 hours at 130 deg core would be sufficient but over-kill. (pun intended). However, it would take a search for me to find that reference again. The core will reach 130 quicker, of course, the higher the kiln temperature. But I'm not the expert you are looking for.

JKJ

Thanks John, if not expert you know a heck of lot and also (as impressively), where to look for the stuff you don't. I have been to Wood Web and will revisit. I don't remember Scott's notes mentioning any timetables.

There is a lot of discussion on Forestry Forum about this issue. The Wood DR Gene Wengert posts there.

Why would you mill logs with bugs?

Quote:

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Originally Posted by gary rosema

Why would you mill logs with bugs?

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Can't see where the OP said he was milling logs with known bugs. When you mill logs you may not know if there are bugs present, specifically the dreaded powder post beetles.

I know for a fact that PPBs can enter the end of a log just moments after sawing - while cutting maple logs outside my shop one day I watched PPB fly across the yard from the woods within seconds and started landing on the end grain to bore into the wood to lay eggs. They located the freshly cut wood by smell. (I immediately sprayed everything with insect killer) When logs are cut then hauled for sawing neither the hauler nor the sawyer can know if bugs are absent or present. A sawyer might spray the endgrain with something like boracare to prevent infestation but by that time it may already be too late. Since PPBs can stay in the log for years before exiting, at which time they can be detected, to be sure the lumber is not infected it is best to treat with heat.

The topic as about insuring no bugs were present in the finished product. He asked about eliminating potential bugs that may or may not be present, verifying core temperatures during heat treating, etc.

But to obliquely answer your completely different question, wood with holes from bugs (but no active bugs) is in demand for artistic reasons. For example, ambrosia maple is sought after for the bug holes and the streaks of discoloration they make. Wormy chestnut is getting hard to find and quite valuable. The bugs are gone but the holes remain. I made these and other things from my dwindling stock of wormy chestnut:

Attachment 451109

JKJ